Mobile communication terminal and electro-acoustic transducer used for the same

ABSTRACT

A portable communication terminal employs an electro-acoustic transducer having openings on the housing. The openings of the transducer are coupled to a housing of the terminal or acoustic pipes unitarily formed with the housing of the transducer. An opening of the acoustic pipe is facing to an opening provided to the housing of the terminal. The terminal uses a transducer including a diaphragm, a cover closely jointed to an outer periphery of the diaphragm and facing to a front face of the diaphragm, and a frame provided to a rear face of the diaphragm. The terminal and the transducer consume less power and yet radiate greater output sound pressure with smaller bodies. They can deliver sound from a display section, so that a user accepts the sound normally.

TECHNICAL FIELD

[0001] The present invention relates to portable communication terminals such as a portable telephone, a personal handy-phone system (PHS), or a portable computer employing a communication modem therein. The present invention also relates to an electro-acoustic transducer (hereinafter referred to as a transducer) to be used in the same portable communication terminals.

BACKGROUND ART

[0002] A conventional portable communication terminal is described with reference to FIGS. 11(a), 11(b), 11(c) and FIG. 12 which illustrate a portable telephone. FIG. 11(a) is a front view of the portable telephone in use. FIG. 11(b) is a side view of the same with partial sectional view therein. FIG. 11(c) is a rear view of the same. FIG. 12 is a side sectional view of a transducer incorporated in the portable telephone.

[0003] In FIG. 11(a), on the front face of portable telephone 10, operating section 10 a including pushbutton digits is prepared, and a transmitter (not shown) is also provided to the front face. Display section 10 b including a liquid crystal display is disposed on an upper part of the front face, and a receiver (not shown) is provided to this upper part. In FIG. 11(c), opening 10 c is provided on the rear face and guides the sound generated by transducer 11 to the outside.

[0004] A structure of transducer 11 is described with reference to FIG. 12. Circular diaphragm 1 generating aerial vibration is supported by frame 2 at its outer periphery with adhesive. Frame 2 includes a plurality of first sound-paths 2 a. An end of voice coil 3 is rigidly fixed to a center portion of diaphragm 1, and both the ends of voice coil 3 are electrically coupled to terminal section 4 disposed at a lower end portion of frame 2.

[0005] A magnetic circuit formed of magnet 5, top plate 6 and yoke 7 is disposed in a recess provided at a center of frame 2. Voice coil 3 is inserted in a space between the outer periphery of top plate 6 and the inner wall of yoke 7.

[0006] Protector 8, to which second sound-paths 8 a are provided, protects diaphragm 1, and forms a housing of the transducer together with frame 2. The foregoing portable telephone thus radiates the sound only delivered from second sound-paths 8 a provided to protector 8 to the outside. On the other hand, the sound delivered from first sound-paths 2 a provided to frame 2 is radiated within portable telephone 10. For that purpose, protector 8 is bonded to the inner wall of phone 10 via a spacer, so that transducer 11 is mounted in phone 10. This structure allows the sound delivered from first sound-paths 2 a and the sound from second sound-paths 8 a of protector 8 to be separated and free from interference.

[0007] The portable telephone has changed its function drastically from a telephone to an information terminal in these days. This change entails the following requirements from the market: more sophisticated performances of the display such as a larger and color display, and better characteristics on an output sound-pressure from the display side as an interactive device. Further, a display of portable communication terminals such as portable telephones accompanies sound more often, such as reproduced sound of a video game, or a tone verifying a operation of pushed buttons.

[0008] Under these circumstances, reproduced sound by a conventional transducer or a conventional mounting structure of the transducer in operating the display lowers a directivity toward the front side of the communication terminal due to diffraction effect, because the sound is delivered only from second sound-paths 8 a. Thus sufficient volume and quality of sound cannot be expected to the front side of the portable telephone. The present invention aims to provide a portable communication terminal that overcomes the foregoing problems.

DISCLOSURE OF THE INVENTION

[0009] A portable communication terminal of the present invention uses a transducer of which opening is formed on a housing thereof. The opening of the transducer is coupled to an acoustic pipe unitarily formed with the housing of the communication terminal or the housing of the transducer. An opening of the acoustic pipe is facing to an opening provided to the housing of the communication terminal. The portable communication terminal of the present invention includes a cover and a frame, which are brought into close contact with the outer periphery of a diaphragm, on a front face and a rear face of the diaphragm respectively. The terminal uses a transducer including at least two openings on the cover and the frame. A transducer used in an embodiment of the present invention has at least two openings or acoustic pipes on either one of the frame or the cover. A transducer used in another embodiment of the present invention includes at least one opening or one acoustic pipe out of two of them on the frame and includes the remaining ones on the cover. The areas of respective openings provided to the cover and the frame are approximately equal to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1(a) is a front view of a portable telephone in use as an embodiment of a portable communication terminal of the present invention.

[0011]FIG. 1(b) is a side view with a half sectional view of the portable telephone shown in FIG. 1(a).

[0012]FIG. 1(c) is a rear view of the same portable telephone.

[0013]FIG. 2 is a side sectional view of a transducer to be used in the portable telephone shown in FIG. 1.

[0014]FIG. 3 shows a perspective exploded view of the transducer.

[0015]FIG. 4(a) is a side sectional view of a transducer in accordance with a second exemplary embodiment of the present invention.

[0016]FIG. 4(b) is a perspective bottom view of the transducer in accordance with the second exemplary embodiment of the present invention.

[0017]FIG. 5(a) is a perspective view of a portable telephone in accordance with the second exemplary embodiment of the present invention.

[0018]FIG. 5(b) is a perspective rear view of the same portable telephone.

[0019]FIG. 5(c) is a front view illustrating a folded status of the portable telephone.

[0020]FIG. 6(a) is a perspective view of a modification of the second exemplary embodiment of the present invention.

[0021]FIG. 6(b) is a perspective rear view of the modification.

[0022]FIG. 7(a) is a perspective view of another modification.

[0023]FIG. 7(b) is a perspective rear view of the same.

[0024]FIG. 7(c) is a sectional view of an essential part of the same.

[0025]FIG. 8 is a perspective view of still another modification.

[0026]FIG. 9(a) is a perspective view of yet another modification.

[0027]FIG. 9(b) is a perspective rear view of the same.

[0028]FIG. 10 is a graph illustrating the characteristics of sound pressure level vs. frequency of the modification shown in FIG. 9.

[0029]FIG. 11(a) is a front view of a conventional portable telephone in use.

[0030]FIG. 11(b) is a side view with a half sectional view of the conventional portable telephone.

[0031]FIG. 11(c) is a rear view of the same.

[0032]FIG. 12 is a side sectional view of a conventional transducer used in the conventional portable telephone.

BEST MODE FOR CARYING OUT THE INVENTION

[0033] An embodiment of the present invention is demonstrated using a portable telephone as an example with reference to the accompanying drawings. Similar elements to those described in the background art have the same reference marks, and the descriptions thereof are omitted here.

[0034] First Exemplary Embodiment

[0035]FIG. 1(a) is a front view of a portable telephone in use as an embodiment of a portable communication terminal of the present invention. FIG. 1(b) is a side view with a partial sectional view of the same. FIG. 1(c) is a rear view of the same. FIG. 2 is a side sectional view of a transducer incorporated in the portable telephone shown in FIG. 1. FIG. 3 shows a perspective exploded view of the transducer.

[0036] In FIG. 1(a) through FIG. 3, first opening 10 d is provided to display section 10 b of portable telephone 12, and second opening 10 e is provided to a rear side of display section 10 b. Transducer 13 built in portable telephone 12 includes second acoustic pipe 13 b, which delivers sound from transducer 13 through first opening 10 d, and first acoustic pipe 13 a, which also delivers sound from transducer 13 through second opening 10 e.

[0037] In the present embodiment, as shown in FIG. 3, first acoustic pipe 13 a is unitarily molded with protector (cover) 8 b which covers a diaphragm, at a time when protector 8 b is resin molded. Second acoustic pipe 13 b is unitarily molded with frame 2 b at a time when frame 2 b is resin molded.

[0038] The acoustic pipes are not necessarily molded with protector 8 b and frame 2 b simultaneously; however, molding at the same time results in lowering the cost. Acoustic pipe sections can be molded at a time when the housing of phone 12 is molded, and the openings are provided to the first and second acoustic pipe sections of transducer 13.

[0039] As shown in FIG. 12, conventional transducer 11 has sound-paths 2 a in frame 2; however, since a magnetic circuit is mounted to frame 2, there is not enough space for sound-paths 2 a. As a result, sound-paths 2 a only have least opening areas so as not to restrict diaphragm 1 from vibrating, and to decrease the sound radiation from sound-paths 8 a of protector 8. In the present embodiment, on the other hand, an opening area of first acoustic pipe 13 a and that of second acoustic pipe 13 b are nearly equal, so that audible difference detected by users can be suppressed. Further, no restrictions as the conventional one allows acoustic pipes 13 a and 12 b to have larger opening areas and to radiate the sound from transducer 13 to the outside efficiently. As a result, a greater sound volume can be expected.

[0040] First acoustic pipe 13 a and second acoustic pipe 13 b are placed symmetrically with respect to diaphragm 1, so that diaphragm 1 is prevented from rolling when it is driven.

[0041] Transducer 13 structured above radiates respective sounds from first opening 10 d and second opening 10 e with 180 degrees phase difference (anti-phase). In other words, this is because acoustic pipes 13 a and 12 b are provided respectively to the front face and the rear face of diaphragm 1. Therefore, around the side faces of the portable telephone, where the sounds from both of the acoustic pipes diffuse and clash with each other, the sounds radiated interfere with each other and attenuate to suppressed sounds. On the other hand, in front of the portable telephone, where a user actually needs the sound, efficiently loud sound can be heard.

[0042] When portable telephone 12 is folded and carried in a user's pocket, second acoustic pipe 13 b is covered by operating section 10 a. Thus the sound radiated from first acoustic pipe 13 a open to the rear face performs paging. In this case, the efficiently loud sound also can be heard similarly to the sound from the front face.

[0043] As discussed above, the portable communication terminal of the present invention radiates loud sound to a direction where the sound is needed, and restricts sound radiation along side faces of a portable telephone where essentially the sound is not needed.

[0044] In the present embodiment, a single transducer 13 radiates the sound through first acoustic pipe 13 a and second acoustic pipe 13 b, then from both of the front and rear faces of portable telephone 12. This structure thus can downsize portable telephone 12. To be more specific, when conventional portable telephone 10 radiates sound from both of the front face and the rear face, and yet it restricts the sound from radiating in other directions, namely, when the conventional phone aims only to improve directivity from the front and rear faces, different transducers are independently used for radiating the sound from the front face and the rear face. In this case, sound signals supplied to the respective transducers have 180 degrees phase-difference from each other. In fact this structure can achieve the objective, however, it needs two transducers, makes the circuit complicated and requires more power, i.e., a larger battery. The present embodiment can overcome those problems.

[0045] Transducer 13 used in the present embodiment has first acoustic pipe 13 a on protector 8 b which works as a part of the housing of transducer 13, and second acoustic pipe 13 b on frame 2 b which is another part of the housing. However, if a space for mounting to portable telephone 12 is limited, only openings instead of pipes can work enough. Whether or not employing the acoustic pipes or a use of a pipe on either one side can be determined accordingly.

[0046] The portable communication terminal in accordance with the present embodiment radiates sounds from both of its front and rear faces to achieve excellent directivity. On the other hand, in other surrounding areas of the terminal, the sounds from the front and rear faces cancel each other because they have 180 degrees phase difference, so that the terminal can restrict the sound radiation from adversely affecting the surroundings.

[0047] Second Exemplary Embodiment

[0048]FIG. 4(a) is a side sectional view of a transducer in accordance with the second exemplary embodiment of the present invention. FIG. 4(b) is a perspective bottom of the transducer. The second embodiment differs from the first one in the following points: First acoustic pipe 32 b and second acoustic pipe 32 c are unitarily formed with resin frame 32 a in which a magnetic circuit is insert-molded. Both of the acoustic pipes are provided under diaphragm 33, so that the sound waves produced and radiated by the vibration of diaphragm 33 passes through tubes 32 b and 32 c are in-phase. First acoustic pipe 32 b radiates the sound downward, and second acoustic pipe 32 c radiates the sound in a side direction. Acoustic pipes 32 b and 32 c thus radiate the sound in two directions different from each other by 90 degrees. Since the sound waves radiated are in-phase, they do not interfere with each other and the sound pressure level can be increased.

[0049] Third Exemplary Embodiment

[0050] FIGS. 5(a) and 5(b) are perspective views of a folding type portable telephone using a transducer in accordance with the second exemplary embodiment of the present invention. FIG. 5(c) is a front view illustrating a folded status of the portable telephone in a user's pocket. Portable telephone 40 includes display section 41 for displaying input information and information obtained through a telephone communication, and operating section 42 through which a telephone number or the like is entered.

[0051] First opening 43 placed at a lower section of display section 41 is coupled to first acoustic pipe 32 b of the transducer demonstrated in the second embodiment. Second opening 44 provided on a lower end face of display section 41 is coupled to second acoustic pipe 32 c of the transducer.

[0052] Those connections between the first and second acoustic pipes of the transducer and the first and second openings of the portable telephone remain the same in the following embodiments and modifications, and the descriptions thereof are omitted hereinafter.

[0053] Since second opening 44 is provided to an end face of the portable telephone, a paging tone can be radiated from this end face when the phone is kept in user's breast pocket as shown in FIG. 2(c). The user thus can notice a calling with ease.

[0054] In the present embodiment, second opening 44 is provided to the lower end face; however, the opening can be provided to a side face. According to the present embodiment, there are less obstacles between the phone and user's ear when the phone is kept in user's pocket comparing with the conventional portable telephone that has a sound radiating path of a transducer in the rear face of the phone. A user thus can notice a paging tone with ease. A situated status of the portable telephone in user's pocket proposes that the second opening be provided to an upper end or a lower end of a rectangular portable telephone so that less obstacles between the phone and user's ear can be expected.

[0055] In the present embodiment, when the portable telephone is folded over, first opening 43 provided to display section 41 is closed when a paging tone is delivered. Thus the sound pressure from second opening 44 increases, and a more remarkable paging tone can be delivered to a user. When a user opens the portable telephone for use, second opening 44 is closed with an end face of operating section 42, so that a sound pressure from first opening 43 can be increased.

[0056] A placement of an opening shown in FIG. 5(a) allows a user to accept the information displayed on display section 41 and the loud sound from opening 43 quite normal because both of the information come from the same direction. The paging tone and the loud sound can be radiated by a single transducer, so that the transducer occupies a smaller space and contributes to downsize the portable telephone.

[0057]FIG. 6(a) through FIG. 9(b) show examples modified from the present embodiment. Each one of the examples includes first openings 45, 47, 49 or 51 that delivers sound upward when the phone is in use, and second openings 46, 48, 50 or 52 that delivers sound from any one of an upper end face, a lower end face, and a side face when the phone is folded. This placement of the openings allows a user to notice a paging tone with ease when the phone is folded over. The arrangement also allows a user to accept sound normally from the first opening because the user hears the sound as if it comes from an operating section or a display toward the user.

[0058] Further, those examples use the transducer in accordance with the second embodiment, namely, first acoustic pipe 2 b is coupled to the first opening and second acoustic pipe 2 c is coupled to the second opening. This single transducer thus can deliver the sound in two directions, and contributes to downsize the portable telephone.

[0059] FIGS. 6(a) and 6(b) show a folding type portable telephone in which first opening 45 is provided to an upper part of operating section 42 and second opening 46 is provided to an upper end face of operating section 42. When the phone is folded, first opening 45 is closed with operating section 42, so that a sound pressure of a paging tone delivered from second opening 46 is increased. Further, when the phone is in use, second opening 46 is closed with a lower end face of display section 12, so that a sound pressure of sound radiated from first opening 45 is increased.

[0060] FIGS. 7(a) and 7(b) show a folding type portable telephone which includes first opening 47 on an upper section of display 41 and second opening 48 on a side face at an upper section. When the phone is folded, first opening 47 is closed with operating section 42, so that a sound pressure of a paging tone delivered from second opening 47 is increased. When the phone is in use, since the radiated sounds are in-phase, an output from second opening 18 passes in front of display 41, which virtually results in increasing the output sound pressure of first opening 47.

[0061] FIGS. 7(a) and 7(b) show the folding type portable telephone; however, as shown in FIG. 7(c) a straight (not folding) portable telephone can have first opening 47 on an upper section of a display section and second opening 48 on a side face at a upper section or on an upper end face. This structure allows a single transducer to deliver a paging tone when the phone is kept and radiate sound from a front face, so that the portable telephone can be downsized. Similarly to the modified example shown in FIGS. 7(a) and 7(b), the outputs from the first and the second openings are in-phase, so that a sound pressure of the output can increase. In the straight portable telephone, the first opening may be provided to a lower face of the operating section and the second opening can be provided to a lower side face or a lower end face. This structure produces the same advantage as what discussed above.

[0062]FIG. 8 shows a folding type portable telephone which has first opening 49 at a lower part of operating section 42 and second opening 50 on a lower end face of operating section 42. When the phone is folded, first opening 49 is closed with display section 41, so that a sound pressure of a paging tone delivered from second opening 50 increases. Further, when the phone is in use, an output from second opening 50 passes in front of display 41, which virtually results in increasing the sound pressure of an output from first opening 49.

[0063] FIGS. 9(a) and 9(b) show a folding portable telephone which has first opening 51 at an upper part of operating section 42 and second opening 52 on a side face of operating section 42 at an upper part. When the phone is folded, first opening 51 is closed with display section 41 so that a sound pressure of a paging tone delivered from second opening 52 increases. Since sounds radiated when the phone is in use are in-phase, an output from second opening 52 passes in front of operating section 12, which virtually results in increasing the sound pressure of output from first opening 21.

[0064]FIG. 10 shows a sound pressure level vs. frequency characteristics at display section 41. Curve X indicates the characteristics of the portable telephone shown in FIG. 5(a) in use. Second opening 44 is closed with the end face of operating section 42. Curve Y indicates the characteristics of the portable telephone shown in FIG. 7(a), and curve Z indicates the characteristics of a conventional portable telephone.

[0065] As FIG. 10 shows, it is confirmed that a structure, having an opening disposed on a display section and another opening, with its open area closed, disposed on a side face when a phone is in use, radiates the highest sound pressure output. A structure, having an opening on a side face and an output therefrom passing in front of a display, is next to the foregoing structure and better than the conventional one.

[0066] As discussed above, a plurality of acoustic pipes are formed in a frame of a transducer, and the acoustic pipes are provided on the same side of a diaphragm of the transducer. A use of this transducer in a portable telephone can increase an output sound pressure and downsize the portable telephone.

[0067] In the first through third embodiments, two acoustic pipes and two openings are used as examples; however, the number of acoustic pipes and openings of a communication terminal can be three or more depending on acoustic characteristics and other requirements. Then various modification can be developed, such as, sound can be radiated from an operating section and both sides simultaneously.

[0068] Further in the previous descriptions, a dynamic transducer is used; however, not to mention, the present invention is not limited to apply to the dynamic transducer, but it is applicable to a piezoelectric transducer. The piezoelectric transducer includes two types, one is to drive a piezoelectric ceramic or a piezoelectric film directly with an electric signal, thereby producing sound, and the other one is to couple a piezoelectric ceramic to a diaphragm for producing sound. A diaphragm using a piezoelectric film or a diaphragm coupled to a piezoelectric ceramic is fit to the present invention among others. A use of such a piezoelectric transducer advantageously decreases power consumption of the portable telephone.

INDUSTRIAL APPLICABILITY

[0069] A portable communication terminal and an electro-acoustic transducer to be used in the terminal of the present invention consume less power, and yet radiate a greater output sound pressure with smaller bodies. The terminal in use delivers sound which virtually comes from a display section so that a user can accept the sound normally. A use of the portable communication terminal and its transducer thus produces great industrial advantage. 

1. A portable communication terminal comprising: an electro-acoustic transducer including one of at least two openings and at least two acoustic pipes, said one of said at least two openings and openings of said at least two acoustic pipes facing to at least two openings provided to a housing of said portable communication terminal.
 2. The portable communication terminal of claim 1, wherein one of said at least two openings and said at least two acoustic pipes are formed on one side of a diaphragm of said transducer.
 3. The portable communication terminal of claim 1, wherein at least one opening or one pipe of said at least two openings and at least two acoustic pipes is formed on one side of a diaphragm of said transducer, and at least another opening or another pipe of said at least two openings and at least two acoustic pipes is formed on another side of the diaphragm.
 4. The portable communication terminal of claim 1, wherein an acoustic pipe unitarily formed with the housing of the terminal is coupled to the openings of said transducer.
 5. The portable communication terminal of claim 1, wherein at least one of the openings provided to the housing is formed on an identical face to a display face of the portable communication terminal.
 6. The portable communication terminal of claim 1, wherein at least one of the openings provided to the housing is open outwardly when the terminal is folded.
 7. The portable communication terminal of claim 6, wherein the opening open outwardly is closed when the terminal is in use.
 8. The portable communication terminal of claim 6, wherein the opening open outwardly is provided to one of a rear face and a side face of the housing, the housing having a display on its front face.
 9. The portable communication terminal of claim 1, wherein the openings of said acoustic pipes are coupled to the openings provided to the housing.
 10. The portable communication terminal of claim 1, wherein said electro-acoustic transducer is one of a dynamic transducer and a piezoelectric transducer.
 11. An electro-acoustic transducer comprising: a frame; a diaphragm attached to said frame at an outer periphery; a cover jointed to entire periphery of said frame, said cover facing a side of said diaphragm, said side being opposite to a side where said frame is attached; and at least two openings provided to at least one of said frame and said cover.
 12. The electro-acoustic transducer of claim 10 further comprising an acoustic pipe coupled to one of said opening.
 13. The electro-acoustic transducer of claim 11 or claim 12, wherein one of said openings and said acoustic pipes are provided to one of said frame and said cover.
 14. The electro-acoustic transducer of claim 11 or claim 12, wherein at least one of said openings and said acoustic pipes are provided to said frame, and at least another one of said openings and said acoustic pipes are provided to said cover.
 15. The electro-acoustic transducer of claim 11 further comprising: a magnetic circuit with a magnetic gap mounted to said frame; and a voice coil inserted into the magnetic gap, wherein said diaphragm is jointed to the voice coil.
 16. The electro-acoustic transducer of claim 11 further comprising a piezoelectric ceramics coupled to said diaphragm.
 17. The electro-acoustic transducer of claim 11, wherein said diaphragm is made of one of piezoelectric ceramics and piezoelectric film. 